I think your underestimating and undervaluing the visibility Monkey Lights provide, and additionally, they're peerless in their category; no other wheel lights that I've seen come close to their brightness.

Regarding balance, care does need to be taken when mounting them, and an opposing pair is best, although a single unit, when properly located near the wheel center, is barely noticeable, particularly at typical, recreational cycling speeds. Bombing down a mountain at 50mph you'd probably notice it more.